Since the beginning of the eighties, when the illness obstructive sleep apnea syndrome was defined, which implies breathing interrupts or breaks in the normal breathing activity during sleep, which is mostly caused by obstruction of the upper air passages, several different methods have been tested, to find out a suitable treatment. Except for operations a so called CPAP (Continous Positive Airway Pressure) method has come into use to an ever increasing extent. Despite some drawbacks, the CPAP- method has shown good treatment results, by the reduction of the day sleepiness which is for example very hazardous when driving a car, and the sleep will be calmer and the characteristic loud snoring will disappear. The CPAP apparatus, which consists of a continously operating radial fan, which is driven by a 100 W electric motor, and a reduction valve, is set on an individual pressure level for respective patient, gives via a tube and a nose mask a continous positive pressure of about 10 mbar, in the breathing passages, which is often satisfactory. Drawbacks as expiration resistance, impossible to use at cold, risk of infection in sinus and ear ducts, drying out of mucous membranes in the nose and mouth at blowing through of excess air (about 4 liters/sec) which the fan delivers, often occurs when the mouth is opened during the sleep, as a rule is tolerated by the patient, but is very troublesome. Despite the relatively high price of the apparatus, this is lower than the cost for the operation, at the same time as considerably less medical treatment is demanded. The level of cost is however of great importance since the calculated need in Sweden is about 100.000 apparatuses, and the cost about 1,2 milliard SEK with present level of price. In addition to this a two days sleeping test at a hospital is required, before the patient can obtain an apparatus for domestic use (OSAS is regarded as a cronical disease). The problem also has another dimension, namely that some traffic accidents, where single road-users as well as drivers of public services are involved has to be charged on the account of sleep apnea, which thus constitute a great latent danger. Very few OSAS- patients are aware of their illness before they have been tested. Fatigue and a bad general condition is often believed to depend on other factors.
In the European patent no 88761 the snoring problem has been attacked by means of nose mask, which is connected to an air pump of high volume type, which during the complete sleeping period continously provides a static air pressure, which is slightly higher than the athmospherical pressure. The drawback of this device is the above mentioned problems. In order to reduce the drying of the mucous membranes, one has even suggested to tape together the mouth during the night, so that the breathing only occurs through the nose, but this drastic measure is for obvious reasons extremely uncomfortable, but illustrates that the side-effects cannot be ignored.
The CPAP- system, which means a continous static air pressure, does not work at the often occuring centrally conditioned apnea contributions in OSAS ( Obstructive Sleep Apnea Syndrome). The static pressure holds the breathing paths open but can not accomplish pulsing breathing activity, which stops at central apneas.
CPAP implies, in addition to said drawbacks that air is pressed into the stomach/intestinal tract at swallowing reflexes, which are provoked by the continous positive pressure, which leads to discomfort. It has also been discovered an increase of the pressure in the cerebrospinal fluid which can have not yet defined consequencies, e.g. balance disorder. A risk of otitis also is present, which might cause a hearing loss.
The device according to said EP 88761 has been developed further, in WO 88/10108, according to which the nose mask is connected to a microphone, the output signal of which via a prcessor unit controls the speed of the motor which drives a fan wheel. In relation to arising to snoring sounds the speed of the motor is increased, and thereby the pressure and the output amount of air. Through this apparatus, during periods when no snoring is present, the continously output amount of air kan be kept on a lower level, whereby the expiration resistance can be kept smaller and thereby also less troublesome. However the tendency of drying up of the mucous membranes is still very troublesome, as well as the increased risk for infection in the sinus and the circumstance that the apparatus cannot be used at common colds. Another drawback is that the impulse generating snoring sounds are individual and irregular, and occur mainly at the end of an apnea period in connection to the sleeping patient himself being able to cure the breathing obstruction. Sound impulses moreover can occur through sleep talking, teeth grinding, caughing and so forth, and externally, why the method is not reliable to cure apnea at the right moment, that is before lack of oxygen occurs in the blood. There is also a risk that that the pressure is elevated at the wrong point of time, so that the sleeping patient is woken up. This system does not supervise loss of breathing, but reacts first on the after-effects (snoring) thereof. Moreover the drawback remains of high energy consumption (portable petrol engines or battery powered devices), even if this has been minimized by the temporarily reduced fan speed.